#include <algorithm>
#include <functional>
#include <iostream>
#include <vector>

using namespace std;

void func(string a, string b, int n) {
  cout << a << ", " << b << ", " << n << endl;
}

int main() {

  auto lambda = [](auto &&a, auto &&b) {
    return func(forward<decltype(b)>(b), forward<decltype(a)>(a), 42);
  };
  lambda("hello", "world"); // 输出 "world, hello, 42"
  return 0;
}